No need to maintain custom URL schemas, as akonadi already has its own, together with various
helper functions to work with it.
Remove UrlRole and use EntityUrlRole instead (use akonadi:?item=... links).
Remove custom internal_link clipboard property, just use the default mechanism for URL setting.
Teach KJotsEdit to insert akonadi links too. This also improves drag-n-drop from treeview,
which is now pasted properly (i.e. title of page/book instead of link itself)